1. Technical Field
The present invention relates generally to electronic device packaging; and, more particularly, it relates to surface acoustic wave filter packaging on a multi-chip module.
2. Related Art
Traditional surface acoustic wave filters are available in relatively expensive ceramic packages. These ceramic packages are expensive not only in terms of initial cost, but they are expensive in terms of subsequent costs such as mounting and subsequent packaging and integration of them into larger scale devices. This relatively expensive purchase cost of conventional surface acoustic wave filters is mostly attributed to the relatively complex packaging of the surface acoustic wave filter that must be performed to ensure its proper performance once it is subsequently integrated into a device. Typically, the surface acoustic wave filter itself is fully enclosed in a ceramic package that itself contains contact pads such that the entire package is capable of being mounted on a substrate. The ceramic package contains, inside of the ceramic package, sufficient space so that the surface acoustic wave filter can properly propagate surface acoustic waves without obstruction. While the operation of these conventionally packaged surface acoustic wave filters is adequate, the cost of procuring them is often prohibitively high for their integration into certain low cost applications. In addition, even for some applications that have the overhead to accommodate their relatively high purchase price, the subsequently associated cost to incorporate them into a device is another cost barrier that must be overcome. These ceramic packages are typically hermetically sealed and surface mounted into their respective devices, and the handling of the relatively delicate ceramic packaging increases the cost of the overall integration of the device into which it is to be installed.
Absent the use of a surface acoustic wave filter that comes pre-packaged in a packaging such as the ceramic packaging described above, the surface acoustic wave filter is commonly incapable of being included into an end product that is to be encapsulated. This is because, using traditional packaging methods, the operation of the surface acoustic wave filter will be greatly compromised by the encapsulation process. This is largely due to the fact that after the encapsulation process has been performed, the surface acoustic waves are unable to propagate on the surface acoustic wave filter due to the obstruction of the material applied during the encapsulation process.
One major problem facing the incorporation of conventional surface acoustic wave filters is how to protect the surface of a surface acoustic wave filter such that it can operate properly even after encapsulation of the surface acoustic wave filter once it has been mounted into a device. Absent the use proper packaging of a surface acoustic wave filter using methods described above such as the ceramic packaging, the conventional art of including surface acoustic wave filters into devices does not permit their proper operation. In addition, the cost associated with their inclusion into many devices is often excessive and prohibitive of their incorporation into various devices. A method to incorporate such devices into so that the difficult cost margins are adequately met simply does not exist in the art. Also, the conventional manner in which surface acoustic wave filters are packaged, in ceramic, is inherently consumptive in real estate on a motherboard or other circuit board, in that, the surface acoustic wave filter requires a fixed amount of space on the board.
Further limitations and disadvantages of conventional and traditional systems will become apparent to one of skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.
Various aspects of the present invention can be found in a wireless transceiver that receives a signal. The wireless transceiver contains a motherboard that itself contains an integrated substrate. On the integrated substrate are numerous circuitries and dies, namely, a switching circuitry, a surface acoustic wave (SAW) filter die, a low noise amplifier (LNA) die, and a mixer die, among other things. The signal that wireless transceiver receives is passed from the switching circuitry to the surface acoustic wave (SAW) filter die, then to the low noise amplifier (LNA) die, and then to the mixer die. From the mixer die, the signal is passed to other circuitry on the motherboard. The surface acoustic wave (SAW) filter die is mounted on the integrated substrate in a xe2x80x9cflip chipxe2x80x9d configuration in accordance with the present invention.
In certain embodiments of the invention, an antenna is used to receive the signal and pass it to the switching circuitry. The wireless transceiver is operable in a variety of different devices such as a wireless communication device or a cellular telephone. In some cases, the signal provided to the wireless transceiver is a speech signal.
The mounting of the surface acoustic wave (SAW) filter die on the integrated substrate in the xe2x80x9cflip chipxe2x80x9d configuration provides an air gap between the surface acoustic wave filter die and the integrated substrate. This air gap ensures proper operation of the surface acoustic wave filter. Also, if desired, a passivation layer composed of a dielectric material is deposited on the surface acoustic wave filter die prior to the surface acoustic wave filter die being mounted on the integrated substrate.
Other aspects of the present invention can be found in a multi-chip module having an integrated substrate and a surface acoustic wave (SAW) filter die. The surface acoustic wave (SAW) filter die is mounted in a xe2x80x9cflip chipxe2x80x9d configuration in accordance with the present invention and it is encapsulated on the integrated substrate.
Additional circuitry is included in the multi-chip module in various embodiments of the invention. For example, the surface acoustic wave filter die is itself contained within a flip mounted circuitry, and a surface mounted circuitry and a chip on-board circuitry are included in the multi-chip module. The surface mounted circuitry contains a switching circuitry, and the chip on-board circuitry contains a low noise amplifier die and a mixer die. Each of the flip mounted circuitry, the surface mounted circuitry, and the chip on-board circuitry is mounted on the integrated substrate. To perform the encapsulation of the surface acoustic wave (SAW) filter die on the integrated substrate, a molding compound is applied. The multi-chip module is operable in a number of electronic devices including a personal communication device. In addition, a passivation layer composed of a dielectric material is deposited on the surface acoustic wave filter die prior to the surface acoustic wave filter die being mounted on the integrated substrate in certain embodiments of the invention.
Other aspects of the present invention can be found in a method to package a surface acoustic wave filter die. The method includes, among other things, passivating a filter side of the surface acoustic wave filter die, then mounting the surface acoustic wave filter die in a flip chip configuration on a substrate, and then encapsulating the surface acoustic wave filter die on the substrate.
In certain embodiments of the invention, the method is performed such that a number of solder balls are applied to the various contacts pads of the surface acoustic wave (SAW) filter die before it is mounted in the flip chip configuration on the substrate. In addition, the various contacts pads on the surface acoustic wave (SAW) filter die are covered before the passivation is performed to the filter side of the surface acoustic wave filter die. The flip chip configuration provides for an air gap between the surface acoustic wave filter die and the substrate. If desired, a dielectric material is applied to the surface acoustic wave filter die to perform the passivation of the filter side of the surface acoustic wave filter die.